1. Field of the Invention
This invention relates to a center pivot irrigation system and more particularly to a center pivot irrigation system whereby the pipe span supported by the last drive unit may be selectively pivoted from its normal aligned relationship with respect to the remainder of the water pipeline to a tucked, trailing or towed position to enable the outer end of the center pivot irrigation system to avoid or by-pass an obstruction, such as trees or a farmstead, which may be in the path of the outer end of the center pivot irrigation system. This invention also relates to an embodiment of the center pivot irrigation system whereby the pipe spans supported by the last drive unit and the next to last drive unit may be selectively pivoted from their normal aligned relationship with respect to the remainder of the water pipeline to a tucked, trailing or towed position to enable the outer end of the center pivot irrigation system to avoid or by-pass the obstruction. Further, the invention relates to an embodiment wherein the pipe spans supported by obstructed intermediate drive units, in addition to the last drive unit and the next to last drive unit, may be selectively pivoted from their normal aligned relationship to a tucked, trailing or towed position to avoid or by-pass the obstruction. The method of operating the systems is also described.
2. Description of the Related Art
Center pivot irrigation systems or machines have been used for many years to irrigate circular areas of a field or the like. In most situations, the circle over which the center pivot irrigation system moves is free from any obstruction such as trees, farmsteads, etc. which protrude into the outer end of the circular arc or path of the center pivot irrigation system which prevents the center pivot irrigation system from making a complete circle. In the past, when such an obstruction was present, the center pivot irrigation system was operated until the outer end of the system came to a position adjacent one side of the obstruction, at which time the drive system and the sprinklers on the system were turned off. The center pivot system was then reversed until the system approached the other side of the obstruction. Such a method has at least two major disadvantages. If the system is reversed, the system must travel over ground which was just previously irrigated which may cause traction problems for the drive wheels of the drive units of the system. Perhaps the main disadvantage of the above-described method is that the center pivot irrigation system moves very slowly so that it may take one or more days before the system will reach the other side of the obstruction which may cause the crop at the other side of the obstruction to suffer from lack of irrigating water. When a lateral move irrigation system encounters one side of an obstruction, it cannot irrigate the area on the other side of the obstruction which dramatically affects the irrigation capability of the system.